I worked at a Sunoco station when I was 18 (1979). I tried to get jobs as a teen where I could learn how to work on cars. The owner let me use the lift at night. The pump had a lever on the side that let you dial the octane requested. Many hot running cars came in to get gas. I saved the round blue medallion off the pump when Sunoco did away with that blend. I think it was 102 octane,also,but hey, at my age,I can't even remember what I had for dinner.LOL

Through our High School years my brothers and I work at our Grandfathers DX Station which changed to Sunoco I believe around 1970. I remember my younger brother burnt the valves in a '68 Chevelle SS396 325 hp. running 260 all the time. I think 102 octane is about right IF memory serves me right. But at my age my memory kind of plays tricks sometimes.

Note that the octane rating systems have changed since the days of the 260 pumps in the 60's-70's; in those days, only the "Research Octane" (RON) number was used, not the lower "Motor Octane" (MON)number. 260 was rated at 102-103 octane by the "Research" method, and 95 octane by the (seldom-used) "Motor" method.

L-88 Corvettes had 12.5:1 compression, and had a sticker on the shift console that said that fuel used must be a minimum of 103 Research Octane or 95 Motor Octane or engine damage could result (from detonation).

In today's world, fuels are identified on the pump by the new "Pump Octane" (PON) number, which adds the RON octane number and the MON octane number together and divides by two (RON + MON/2). If you could buy 260 today, the pump would show 99 octane (103 + 95/2).

Good premium fuel back in the day was rated at 97-98 octane by the "Research" method, and at 88 octane by the "Motor" method; with today's mandated PON pump-octane formula, that converts to a 93 octane PON number that would be on the pump today. Today's 93 octane fuel is the same as yesterday's 97-98 octane fuel; you'll find 98 octane on the premium pump in Europe today, as they only use the "Research" octane number on the pump.

When we built our retirement home/garage in 2000, my wife bought me a restored Sunoco 260 dial-your-octane pump as a housewarming gift for the garage, but she forgot the 8,000-gallon underground tank full of 260 to go with it.

...Just like John said. All the confusion comes from the "custom blending" capabilities of the Sunoco "Dial A Grade" pumps that offered "octane grades" from 190 to 260 --subregular to super-premium, whose numbers didn't actually reflect the MON octane ratings. It always struck me as more about marketing than performance. I do remember, however, that they sold good gas.

BTW, as a teenager, I always wanted to look inside those Dial A Grade pumps to see how they blended all those grades...

Octane is an 8-hydrocarbon chain and is more compressible without spontaneous detonation. Heptane is a 7-hydrocarbon chain. It is very volatile and it ignites spontaneously under very little compression. So 87 grade gasoline is 87% octane & 13% heptane which ignites at a given compression level. 87 grade is known as Regular gasoline.

Basically what you need to know is that you will get the maximum power from running the lowest octane without detonation... so if you can run 87 octane run that. The higher grade octanes are only to prevent spontaneous detonation (aka engine knock - very bad).

As you probably know most Chevy Camaro's had average to high compression ratios (i.e. about 9:1 I think for the 327, the L78 11:1, the L72 12:1, L88 & ZL1 12.5:1). The 10:1 and higher ratios would not run without detonation under 93 octane gasoline and that might have been pushing it for the 427's.

The higher the compression ratio the more power the engine made. (the 11:1 and higher stuff was really Hi-Perf race-car levels.) If I remember right, GM required these engines to run on a minimum of 98 octane gasoline; aka Super gasoline, Premium gasoline, etc...

" BTW, as a teenager, I always wanted to look inside those Dial A Grade pumps to see how they blended all those grades... "

Hi Phill,

I believe it was done the same as today, basically with a blending type valve. Turning the dial selected the preset blend ratio. So a selected grade would be made up of so much high test (Super gas) and so much of the regular gasoline... just roughly figuring I think it goes like this; to get 89 octane the blender takes a preset ratio at about 40% 93 octane and then take about 60% regular 87 octane blending them together for the 89 octane. (It might be more complicated than that but I think that is the approach.) Joe

PS - in the photo just above the center filter I think is the metering blend valve... the blue thing to the left is a Wayne vacuum motor used for collecting the gasoline vapors from your cars tank as you pumped gas...